application vs. request scope and performance

[Tom Butler]

The initial page of my app is a search page.  The app may have up to 100+ concurrent users.   I was considering whether it would be better for performance to set the backing bean for the search page within the application scope (bean is multi-threaded and same bean accessed by all users), or, request scope (bean created/removed for each user accessing the search page)?    Any recommendations?  I see benefits of application scope being bean is already loaded in memory, but may cause performance issues if too many users access at once – is there anyway to have multiple copies of an application scope bean to improve performance?   Sorry these are probably more general java questions (within a JSF app) – let me know if there is a more appropriate forum to post to.   Thanks Tom